In a typical power distribution system, such as for residential homes, a fuse panel with a number of fuses are used. The trip value of each fuse is selected to protect each load device connected to the fuse. When a new load device is to be connected to the panel, a free fuse with a proper trip value for the new load device is selected.
Fuse panels of today are based on a number of different technologies such as melting wire types, heat activated types and electronic types. No matter the type, the fuse “trips” or breaks the circuit to the load device when the current provided to the load device exceeds the trip value.
FIG. 12 illustrates a conventional fuse panel 1200 that includes a plurality of individual fuses 1210. In this particular example, there are six (6) fuses 1210 with differing trip values. The first two fuses have the trip values set at 2 amperes (or 2 A), the second 2 fuses have their trip value set at 5 A and the third set of fuses have their trip value set at 10 A. Each fuse provides power from an external power source 1240 to the respective load devices 1250.
The fuses 1210 can be electronic type fuses. FIG. 13 illustrates a conventional electronic fuse 1210. The conventional electronic fuse 1210 includes an electronic switch 1310 coupled to a shunt 1330 to deliver power from the external source connected at input 1212 (see also FIG. 12) to the load device connected at output 1214. The electronic fuse 1210 also includes a voltage comparator 1320 that measures a voltage drop across the shunt 1330. The voltage drop across the shunt 1330 is related to an amount of current flowing through the shunt 1330 to the load device 1250. If the voltage drop across the shunt 1330 is at or above a threshold level, the comparator 1320 outputs a signal to the electronic switch 1310 to turn off. By setting the threshold voltage, an appropriate trip value is set for the electronic fuse 1210.
A major disadvantage with the conventional fuse and fuse panels is that the trip value of each fuse must be determined during the production of the panel and remains fixed. For electronic fuses such as those illustrated in FIG. 13, threshold voltage is fixed during the production. This requires that each panel be tailored for a number of load devices at specific current values. This creates a problem when a new load device is desired to be added but there is no free fuse available with the correct trip values. Referring back to FIG. 12, it is seen that both 2 A fuses are already occupied. If another 2 A load device is desired to be connected, it will impossible with the conventional fuse panel. This is despite the fact that there are fuses with other trip values available such as the 5 A and 10 A fuses.
Conventionally, this problem can be addressed by rebuilding the panel or by adding a new panel altogether. Both of these solutions are inefficient and costly.